Conducts a GPIB (IEEE-488) Parallel Poll and returns status.
PPOLL( {@io-path | interface-select-code} )
Usage:
PPOLL(8)
PPOLL(@Gpib)
IF BIT (PPOLL(10),3) THEN Start
Description:
A GPIB parallel poll is performed and an 8-bit status message from the GPIB is returned. If the computer is not the active controller an error is generated. The I/O path or interface select code must refer to the GPIB interface.
The bus action is as follows: ATN and EOI are set for ≥25 microsec., one byte of data is read from the bus, EOI is released, and ATN is restored to its previous state.